Note extent of farm (6)
I believe the answer is:
grange
'farm' is the definition.
(I know that grange is a type of farm)
'note extent' is the wordplay.
'note' becomes 'g' (musical note).
'extent' becomes 'range' (range is a kind of extent).
'g'+'range'='GRANGE'
'of' is the link.
(Other definitions for grange that I've seen before include "farming complex" , "Country house with attached farm buildings" , "Farmhouse" , "Country house and surrounding buildings" , "Ganger in country house with farm buildings" .)